Nippondenso Co., Ltd.

Katuhiko Kodama

Toshio Kondo

Hiroshi Haraguchi

Hiroshi Tamura

Toshiaki Mizuno

A method of controlling the air fuel ratio in internal combustion, engines, comprising the steps of: updating first learning terms at a first learning speed in response to a signal from the air-fuel-ratio sensor and respectively storing them in a reloadable memory device, the first learning terms being provided for respective different ranges corresponding to different engine temperature and related to factors causing variation in air-fuel ratio in such a manner that the air-fuel-ratio variate of the variation varies depending upon the engine temperature; updating second learning terms at a second learning speed which is higher than the first learning speed in response to a signal from the air-fuel-ratio sensor and storing them in the reloadable memory device, the second learning terms being related to factors causing variation in air-fuel ratio in such a manner that the air-fuel-ratio variate of the variation varies in a substantially uniform manner with respect to the engine temperature; and determining the transient learning value on the basis of the first learning terms dependent on the engine temperature and stored in the memory device and of the second learning terms stored in the memory device, and correcting the transient correction value in accordance with the transient learning value thus determined.

Method of controlling air-fuel ratio

In an abnormality detection apparatus for vehicle engines, a deceleration discriminating circuit discriminates a deceleration state of a vehicle engine on the basis of a running state of the engine detected by a running state detector for detecting a running state of the vehicle engine. When the deceleration discriminating circuit determines that the engine is being in deceleration state, a comparing circuit compares a vehicle speed detected by a vehicle speed detector with a predetermined value. An abnormality deciding circuit is responsive to a comparison result signal from the comparing circuit to decide abnormality of the vehicle speed detector.

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Obu, Japan

Katuhiko Kodama